| 摘要 |
PURPOSE:To enable direct indication of a measured value of a wave head length of a lightning surge by detecting the first transition of the surge and reaching the maximum in the instantaneous value thereof to count the time between the two detections. CONSTITUTION:An input circuit 2 outputs a voltage to be measured proportional to the instantaneous value of a lightning surge. A high speed comparator circuit A1 inverts the output level the moment the instantaneous value of the voltage to be measured, which permits a level conversion circuit 4 to output a signal of a high level to open an AND gate and a reference time signal 10 is input into a counter 12. On the other hand, a high speed peak hold circuit 3 whose output is arranged to follow the voltage to be measured retains the maximum value (e) when the voltage reaches it. A high speed comparator circuit A2 inverts the output potential the moment the voltage to be measured falls slightly below the voltage (e). This enables a level conversion circuit 6 to output a signal of a high level to reset R-SFF thereby halting the counting of the counter 12. Thus, the counter 12 counts the length of the wave head which will be displayed. |
